Placental location in pregnancies following Cesarean section

Ultrasonic placentography was used to compare placental location in patients who had undergone previous Cesarean sections with those who had had vaginal deliveries. Results indicated that: (1) placental location was not influenced by existing uterine scars; (2) anterior uterine wall implantations occur with sufficient frequency (35%) to warrant ultrasonic placentography prior to third trimester amniocentesis for fetal maturity studies; and (3) lower anterior uterine segment implantations occur with sufficient frequency (8%) to warrant ultrasonic placentography prior to surgical entry of the lower uterine segment.